X-ray fluorescence (XRF) mapping for anode inspection

Abstract

Aspects of the disclosure include leveraging an X-ray fluorescence (XRF) mapping of copper current collectors for non-contact, non-destructive, in-line quality inspections of thin lithium metal anodes. An exemplary method can include receiving an electrode at a detection surface of the XRF detector. The electrode can include the lithium anode on a surface of a current collector. X-rays are passed through the lithium anode and into the current collector and the intensity of characteristic radiation returning from the current collector is measured at the XRF detector. A lithium anode characteristic can be inferred based on the measured intensity of characteristic radiation from the current collector.

What is claimed is: 
     
       1. A method for indirectly characterizing a lithium anode, the method comprising:
 receiving an electrode at a detection surface of an X-ray fluorescence (XRF) detector, the electrode comprising the lithium anode on a surface of a current collector, the current collector comprising a copper current collector, the lithium anode comprising a thin lithium anode having a thickness of less than 20 microns; 
 passing X-rays through the lithium anode and into the current collector; 
 measuring, at the XRF detector, an intensity of characteristic radiation from the current collector, the characteristic radiation comprising fluorescing L shell characteristic radiation; 
 generating a current collector mapping from the measured intensity of characteristic radiation; and 
 determining, from the current collector mapping, a lithium anode characteristic based on the measured intensity of characteristic radiation from the current collector. 
 
     
     
       2. The method of  claim 1 , wherein the lithium anode characteristic comprises one or more of lithium thickness, lithium thickness variation, a presence of a surface defect, and a presence of an internal defect. 
     
     
       3. The method of  claim 1 , wherein determining a lithium anode characteristic comprises correlating the measured intensity of characteristic radiation to a thickness of lithium according to the formula t=ln(I 0 /I)*sin(β)*(μ/ρ) −1 , where t is the thickness of lithium, I 0  is a baseline intensity with no lithium coating, I is the measured intensity of characteristic radiation, β is a detector angle, and (μ/ρ) is a mass absorption coefficient for lithium. 
     
     
       4. The method of  claim 1  further comprising measuring, at the XRF detector, a second intensity of a second characteristic radiation. 
     
     
       5. The method of  claim 4  further comprising characterizing a presence of a chemical impurity based on the measured second intensity of second characteristic radiation. 
     
     
       6. The method of  claim 1 , wherein characterizing the lithium anode comprises a non-contact, non-destructive, in-line process. 
     
     
       7. The method of  claim 6 , wherein continuous or near-continuous lithium anode characterization occurs by moving the lithium anode across the detection surface of the XRF detector. 
     
     
       8. The method of  claim 1  further comprising positioning a second XRF detector on an opposite surface of the lithium anode from the XRF detector. 
     
     
       9. The method of  claim 1  further comprising positioning a plurality of second XRF detectors on a same side of the lithium anode for edge-to-edge variability characterization. 
     
     
       10. A method for indirectly characterizing lithium anode defects, the method comprising:
 creating a known defect in a reference lithium anode, wherein the known defect comprises one of an internal void, a surface dent, and a surface bump in the reference lithium anode; 
 receiving a reference electrode at a detection surface of an X-ray fluorescence (XRF) detector, the reference electrode comprising the reference lithium anode on a surface of a current collector, the current collector comprising a copper current collector, the reference lithium anode comprising a thin lithium anode having a thickness of less than 20 microns; 
 passing X-rays through the reference lithium anode and into the current collector; 
 measuring, at the XRF detector, a local intensity of characteristic radiation from the current collector at a region corresponding to the known defect, the characteristic radiation comprising fluorescing L shell characteristic radiation; 
 generating a current collector mapping from the measured intensity of characteristic radiation; and 
 determining, from the current collector mapping, a correlation between the measured local intensity of characteristic radiation and one or more parameters of the known defect. 
 
     
     
       11. The method of  claim 10 , wherein the one or more parameters of the known defect include a shape, a depth, a location, or a size of the known defect. 
     
     
       12. The method of  claim 10  further comprising creating a second known defect in the lithium anode, wherein the second known defect is of a different type than the known defect. 
     
     
       13. The method of  claim 12  further comprising measuring, at the XRF detector, a second local intensity of characteristic radiation from the current collector at a second region corresponding to the second known defect. 
     
     
       14. The method of  claim 12  further comprising determining a correlation between the measured second local intensity of characteristic radiation and one or more parameters of the second known defect. 
     
     
       15. The method of  claim 10 , further comprising receiving an active electrode at the detection surface of the XRF detector, the active electrode comprising a lithium anode on a surface of a current collector. 
     
     
       16. The method of  claim 15 , further comprising passing X-rays through the lithium anode and into the current collector of the active electrode. 
     
     
       17. The method of  claim 16 , further comprising measuring, at the XRF detector, an intensity of characteristic radiation from the current collector of the active electrode. 
     
     
       18. The method of  claim 17 , further comprising characterizing a defect in the lithium anode of the active electrode based on the measured intensity of characteristic radiation from the current collector in the active electrode and the determined correlation between the measured local intensity of characteristic radiation and one or more parameters of the known defect in the reference electrode.